The objective of the present investigations will be to isolate, purify and characterize a concanavalin-A adsorbing compound, presumably a glycoprotein, which appears to be responsible for the conversion of the insulin receptor from a low molecular weight species which exhibits no cooperativity of binding to a high molecular weight component which exhibits a high-affinity, low capacity site and a low-affinity, high capacity site, the kinetics of which are concomitant with negative cooperativity. We intend to use simian viral transformed fibroblasts, from which we have successfully extracted the insulin receptor, rat liver and human placenta, from which we have also been successful in solubilizing the receptor, as a source of both the insulin receptor and the glycoprotein. The major methods to be applied will be column chromatography, sucrose gradient density centrifugation, electrophoresis and affinity column chromatography in an attempt to (1) determine a faster method of assay for the glycoprotein than the one presently being employed and (2) purify the glycoprotein to ascertain the stoichiometry of the reactions.